This invention relates generally to a photographic system of the scanning type in which the parts of the subject being photographed are illuminated by a moving radiant energy beam, and more particularly to the utilization of multi-spectral color and "false color" photography in such a photographic system.
This invention is an improvement over U.S. Pat. No. 3,316,348 issued Apr. 25, 1967. In the area of tactical reconnaissance, there is an urgent need for sensor techniques which are suitable for detection and identification of targets of military significance such as enemy personnel, tanks, trucks, missile launch sites, stores, etc. Because a large part of emeny activity occurs at night, airborne sensors nighttime operation are increasingly important. As shown in U.S. Pat. No. 3,316,348 it has been possible to make a photographic recording of a large dark object, such as a long strip of terrain as viewed from an airplane at night, by means of an extremely narrow radiant energy beam (such as produced by a laser) which beam is caused to line scan the object, for example, in a rectilinear pattern. By causing the scan movement of the illuminating laser light beam and the scanning of the photographic film by a second light source to be synchronous, the photographic record will accurately reproduce the subject by a photograph. The problem arising in U.S. Pat. No. 3,316,348 and in other prior art devices is that single color line scan is utilized in obtaining this photographic information. The result is imagery where targets of interest are distinguished and identified only if sufficient contrast and resolution are available and are depicted as one shade of gray against the background of another shade of gray. The single color line scan also falls short wherever it is necessary to make rapid recognition and detection of camouflaged areas in which these gray areas are virtually indistinguishable.